The solar system and time Flashcards
Aphelion is the point during orbit around the sun where -
the earth is farthest from the sun
Perihelion is the point during orbit around the sun where -
the earth is closest to the sun
Aphelion occurs approximately in -
July 4th
Perihelion occurs approximately in -
January 4th
The change of seasons is due to?
The inclination(tilt) of the earth
The earth’s spin axis(approximately N/S, in reference to the orbital plane around the sun, is tilted at an angle of -
66.5 degrees.
In the NH winter solstice occurs -
on 21st of December
In the SH winter solstice occurs -
on 21st of June
In the NH summer solstice occurs -
on 21st of June
In the SH summer solstice occurs on -
21st of December
In the SH autumn equinox occurs on -
March 21st
In the NH spring equinox occurs on -
March 21st
In the SH spring equinox occurs on -
September 21st
In the NH autumn equinox occurs on -
September 21st
If the North Pole is tilted at its maximum possible angle towards the sun, which hemisphere will experience winter?
Southern Hemisphere
If the North Pole is tilted at its maximum possible angle away from the sun, which hemisphere will experience winter?
Northern Hemisphere
The apparent solar day is of -
variable length and not suitable for time keeping
An apparent solar day is always longer than -
a sidereal day
The mean solar day(exactly 24 hours) is used as the -
basis for time keeping
The type of “day” definition that is not constant?
An apparent day
1 hour of a mean solar day = how many degrees?
15 degrees
LMT(local mean time) is the same for a given meridian irrespective of -
latitude
To convert LMT to UTC/Zulu/GMT time, the mnemonic is?
Longitude East, UTC least
Longitude West, UTC best
UTC =
GMT
GMT =
UTC
AM and PM means -
Ante-meridian and post meridian
AM and PM:
Morning will be during =
Ante-meridian
AM and PM:
Afternoon will be during =
Post-meridian
UTC is 13:23:00, determine the standard time at Durban(30 degrees 57 minutes east). The STF is 2
The STF is either added or subtracted to/from UTC in order to find the standard time. No need to find the arc time.
East UTC least
West UTC best.
Define standard time -
Standard time is a further development of zone time to allow a country to adopt one time as its standard. South Africa is in fact a case in point. Most of the republic falls into the zone which is UTC + 2 hours, but some parts - notably cape town - are on zone UTC + 1 hour. To make life simple, south africa has adopted UTC + 2 hours for the whole country. This will be expressed as Standard Time Factor of 2. To determine whether to add or subtract the STF, the longitude of the position in relation to the Greenwich meridian must be known.
always remember: East UTC least. West UTC best
The international date line is =
The Ante-meridian(180E/W)
Local mean time noon will occur -
Local mean time sunset and sunrise will occur -
at 12:00, on any latitude for the same meridian.
at the same time only for the same meridian and on the same parallel.
LMT is relative to the -
local meridian.
LMT between 30°00’ E and 60°00’ E will differ by -
360/24 = 15° per hour.
30°(long difference) / 15° = 2 hours.
The local mean time will differ by 2 hours.
LMT at A 30°00’ W = 13:00. What is the LMT at B 20°00’ W?
This problem can be solved by only using arc time and a little logic to figure which time is before which, but using this method for more complex problems is not easier. Convert to UTC.
Since A is to the west of UTC, we need to add to the LMT(west UTC best):
30° / 15° = 2 hours.
13:00 + 2 = 15:00 UTC
B is also to the west:
20° / 15 = 1:20m.
Since we already have a UTC of 15:00, we need to reverse the west best/east least mnemonic.
15:00 - 1:20 = 13:40 LMT.
LMT at B = 13:40.
